#include <stdio.h>
#include <string.h>
#include <stdlib.h>

char * inKtu(char * str) {
	int A[255];
	int j = 0;
	char * kq = (char *) malloc(255); // Khai bao string.s
	for (int i = 0; i < 255; i++) A[i] = 0;
	for (int i = 0; i < strlen(str); i++) {
		if (str[i] == ' ') continue;
		if (A[str[i]] == 0) { // Ky tu cung dc hieu ngam la so!
			A[str[i]] = 1;
			kq[j++] = str[i];
		}
	}
	kq[j] = '\0';
	return kq;
}

int main() {
	char str[] = "Hello World";
	char * kq;
	kq = inKtu(str);
	printf("%s",kq);
}